In the building and construction trade there is an ongoing continuing search for inexpensive materials which can be used as substitutes for more expensive materials or materials otherwise in more limited supply. In a search for alternative materials, one must of course give consideration to whether a substitute material will provide the requisite performance characteristics. Such characteristics include strength, resilience, uniformity, workability, weatherability, density, creep, thermal insulation value and expansion coefficient.
Of course, any substitute material must be able to be produced in sufficient quantity to meet the demands of the applications to which it is to be applied. Thus, it is desirable to be able to produce a building material in such quantity.
It is also desirable to be able to produce a building material quickly and efficiently, to save energy and labor. Typical building materials, such as stone, wood or metal must be harvested, transported and finished before being used. Therefore it is an object of the present invention to produce building materials that can be ready made for particular applications, and which can be produced within a range of physical characteristics such as those mentioned above.
Another desirable characteristic in a building material is that the material be workable, or at least be easily made workable. That is, it is desirable that the material be amenable to cutting and/or drilling; and be capable of receiving nails, screws, or fittings therefor; and be suitable for adhesive bonding. Thus it is an object of the present invention to produce a material which may be worked in a manner customary to the building trade and required in a variety of potential applications. It is also preferred that building materials be resistant to degrading environmental effects, such as water, sunlight, temperature change, abrasion, pests such as termites, etc. Therefore, another object of the present invention is to allow the production of building materials which may be readily used in a wide variety of interior and exterior settings while being relatively unaffected by such environmental effects, without the need for protective treatments such as staining, impregnation with chemicals, etc.
It is also an object of the present invention to be able to produce building materials which have consistent and reproducible mechanical and physical characteristics as outlined above.
Another present day concern is for the environment. Much attention has been focused on the need to recycle waste materials economically. This has meant finding uses for waste stream materials which are both safe and require little processing to the waste material to place it a useable form. It is therefore an object of the present invention to provide a method which can be used to produce a useful product from relatively unadulterated waste materials; and which is safe for those making use of such a product. Also, there has been concern for the long term conservation of harvestable forests. Thus, an object of the present invention is to provide a building material that could be used in place of scarce resource materials, such as wood or structural metals.
For instance, in searching for wood substitutes, consideration usually must be given to whether the substitute material will provide those minimum characteristics which will allow it to perform in a given desired application. One area in which materials of the present application might be applied is as substitutes for the high grade wood used in door and window frames, furniture, and the like. Such high grade wood is in limited supply and currently limits the total production of door and window frames. It is relatively uniform in its characteristics, being generally free of knots, blemishes and other discontinuities in the wood grain, and is relatively both light and strong. Even high grade wood however does vary in its physical characteristics. Also, wood is subject to degrading environmental effects.
Accordingly, it is an object of one embodiment of the present invention to produce a substitute building material for high grade framing wood which conforms to its physical characteristic profile while being relatively inexpensive to produce. It is also possible through the present invention to produce such a substitute building material in quantities which are sufficient to fill the need for such a material.
As to the production of a material which may vary in its physical characteristics, it is desirable to be able to produce a material which might have its physical characteristics adjusted depending, for instance, which particular grade of wood or strength of wood is to be replaced by the substitute material. It is also a goal of the present invention to produce a wood substitute material which is relatively unaffected by degrading environmental factors.
With regard to the production of composite materials in general, one obstacle to be overcome is to have the component materials bond to one another. Another related concern is to provide bonding which will allow thermal expansion and contraction without causing separation of the bound materials.
The process of producing composite materials is even further complicated when it is to be carried out in a continuous process, such as in an extrusion process. In such processes, it is important that the component materials be able to go through the "mating" process wherein the heating, cooling, cross-linking and dimensional stabilization of the component materials are coordinated and calibrated. For instance, in continuous extrusion processes, it is necessary that the cooling thermoplastic component be retained in the desired finished profile in the calibration zone until it has formed a durable "skin" that will resist damage in downstream processing steps. Additionally, the thermosetting core must cure sufficiently and have sufficient hot strength during this same retention period that it will not alter the profile defined by the thermoplastic component after leaving the calibration zone. It is therefore important that the uncured/uncooled composite have sufficient hot strength to retain the desired shape in the finished product. Accordingly, it is necessary to be able to provide such calibration and coordination if such component materials are to be made in a continuous process as described more fully herein.
Finally, it is always desirable to develop manufacturing processes which are able to use their own waste material by recycling. This is one of the features provided in the present invention.
Although the advantages and goals of the present invention are described with reference to building materials, particularly as a substitute for wood, the present invention is not limited to either general or specific uses. Indeed, the potential uses of the present invention are numerous as may become apparent to one of ordinary skill in the fields of endeavor to which the present invention might be applied.
Accordingly, additional advantages or the solution to other problems may become apparent to one of ordinary skill in these arts from the present disclosure or through practice of the present invention.